add key to FileInfo

MatchingKey is not the thing to use when matching on actual worktreee
files.

Fix reversion in 8.20201116 that made include= and exclude= in
preferred/required content expressions match a path relative to the current
directory, rather than the path from the top of the repository.

Command/Import.hs

@@ -241,6 +241,7 @@ startLocal o addunlockedmatcher largematcher mode (srcfile, destfile) =
 		let mi = MatchingFile $ FileInfo
 			{ contentFile = Just srcfile
 			, matchFile = destfile
+			, matchKey = Nothing
 			}
 		lockingfile <- not <$> addUnlocked addunlockedmatcher mi
 		-- Minimal lock down with no hard linking so nothing